Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
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linux
1# SPDX-License-Identifier: GPL-2.0
2menu "Firmware loader"
3
4config FW_LOADER
5 tristate "Firmware loading facility" if EXPERT
6 select CRYPTO_LIB_SHA256 if FW_LOADER_DEBUG
7 default y
8 help
9 This enables the firmware loading facility in the kernel. The kernel
10 will first look for built-in firmware, if it has any. Next, it will
11 look for the requested firmware in a series of filesystem paths:
12
13 o firmware_class path module parameter or kernel boot param
14 o /lib/firmware/updates/UTS_RELEASE
15 o /lib/firmware/updates
16 o /lib/firmware/UTS_RELEASE
17 o /lib/firmware
18
19 Enabling this feature only increases your kernel image by about
20 828 bytes, enable this option unless you are certain you don't
21 need firmware.
22
23 You typically want this built-in (=y) but you can also enable this
24 as a module, in which case the firmware_class module will be built.
25 You also want to be sure to enable this built-in if you are going to
26 enable built-in firmware (CONFIG_EXTRA_FIRMWARE).
27
28config FW_LOADER_DEBUG
29 bool "Log filenames and checksums for loaded firmware"
30 depends on DYNAMIC_DEBUG
31 depends on FW_LOADER
32 default FW_LOADER
33 help
34 Select this option to use dynamic debug to log firmware filenames and
35 SHA256 checksums to the kernel log for each firmware file that is
36 loaded.
37
38config RUST_FW_LOADER_ABSTRACTIONS
39 bool "Rust Firmware Loader abstractions"
40 depends on RUST
41 select FW_LOADER
42 help
43 This enables the Rust abstractions for the firmware loader API.
44
45if FW_LOADER
46
47config FW_LOADER_PAGED_BUF
48 bool
49
50config FW_LOADER_SYSFS
51 bool
52
53config EXTRA_FIRMWARE
54 string "Build named firmware blobs into the kernel binary"
55 help
56 Device drivers which require firmware can typically deal with
57 having the kernel load firmware from the various supported
58 /lib/firmware/ paths. This option enables you to build into the
59 kernel firmware files. Built-in firmware searches are preceded
60 over firmware lookups using your filesystem over the supported
61 /lib/firmware paths documented on CONFIG_FW_LOADER.
62
63 This may be useful for testing or if the firmware is required early on
64 in boot and cannot rely on the firmware being placed in an initrd or
65 initramfs.
66
67 This option is a string and takes the (space-separated) names of the
68 firmware files -- the same names that appear in MODULE_FIRMWARE()
69 and request_firmware() in the source. These files should exist under
70 the directory specified by the EXTRA_FIRMWARE_DIR option, which is
71 /lib/firmware by default.
72
73 For example, you might set CONFIG_EXTRA_FIRMWARE="usb8388.bin", copy
74 the usb8388.bin file into /lib/firmware, and build the kernel. Then
75 any request_firmware("usb8388.bin") will be satisfied internally
76 inside the kernel without ever looking at your filesystem at runtime.
77
78 WARNING: If you include additional firmware files into your binary
79 kernel image that are not available under the terms of the GPL,
80 then it may be a violation of the GPL to distribute the resulting
81 image since it combines both GPL and non-GPL work. You should
82 consult a lawyer of your own before distributing such an image.
83
84 NOTE: Compressed files are not supported in EXTRA_FIRMWARE.
85
86config EXTRA_FIRMWARE_DIR
87 string "Firmware blobs root directory"
88 depends on EXTRA_FIRMWARE != ""
89 default "/lib/firmware"
90 help
91 This option controls the directory in which the kernel build system
92 looks for the firmware files listed in the EXTRA_FIRMWARE option.
93
94config FW_LOADER_USER_HELPER
95 bool "Enable the firmware sysfs fallback mechanism"
96 select FW_LOADER_SYSFS
97 select FW_LOADER_PAGED_BUF
98 help
99 This option enables a sysfs loading facility to enable firmware
100 loading to the kernel through userspace as a fallback mechanism
101 if and only if the kernel's direct filesystem lookup for the
102 firmware failed using the different /lib/firmware/ paths, or the
103 path specified in the firmware_class path module parameter, or the
104 firmware_class path kernel boot parameter if the firmware_class is
105 built-in. For details on how to work with the sysfs fallback mechanism
106 refer to Documentation/driver-api/firmware/fallback-mechanisms.rst.
107
108 The direct filesystem lookup for firmware is always used first now.
109
110 If the kernel's direct filesystem lookup for firmware fails to find
111 the requested firmware a sysfs fallback loading facility is made
112 available and userspace is informed about this through uevents.
113 The uevent can be suppressed if the driver explicitly requested it,
114 this is known as the driver using the custom fallback mechanism.
115 If the custom fallback mechanism is used userspace must always
116 acknowledge failure to find firmware as the timeout for the fallback
117 mechanism is disabled, and failed requests will linger forever.
118
119 This used to be the default firmware loading facility, and udev used
120 to listen for uvents to load firmware for the kernel. The firmware
121 loading facility functionality in udev has been removed, as such it
122 can no longer be relied upon as a fallback mechanism. Linux no longer
123 relies on or uses a fallback mechanism in userspace. If you need to
124 rely on one refer to the permissively licensed firmwared:
125
126 https://github.com/teg/firmwared
127
128 Since this was the default firmware loading facility at one point,
129 old userspace may exist which relies upon it, and as such this
130 mechanism can never be removed from the kernel.
131
132 You should only enable this functionality if you are certain you
133 require a fallback mechanism and have a userspace mechanism ready to
134 load firmware in case it is not found. One main reason for this may
135 be if you have drivers which require firmware built-in and for
136 whatever reason cannot place the required firmware in initramfs.
137 Another reason kernels may have this feature enabled is to support a
138 driver which explicitly relies on this fallback mechanism. Only two
139 drivers need this today:
140
141 o CONFIG_LEDS_LP55XX_COMMON
142 o CONFIG_DELL_RBU
143
144 Outside of supporting the above drivers, another reason for needing
145 this may be that your firmware resides outside of the paths the kernel
146 looks for and cannot possibly be specified using the firmware_class
147 path module parameter or kernel firmware_class path boot parameter
148 if firmware_class is built-in.
149
150 A modern use case may be to temporarily mount a custom partition
151 during provisioning which is only accessible to userspace, and then
152 to use it to look for and fetch the required firmware. Such type of
153 driver functionality may not even ever be desirable upstream by
154 vendors, and as such is only required to be supported as an interface
155 for provisioning. Since udev's firmware loading facility has been
156 removed you can use firmwared or a fork of it to customize how you
157 want to load firmware based on uevents issued.
158
159 Enabling this option will increase your kernel image size by about
160 13436 bytes.
161
162 If you are unsure about this, say N here, unless you are Linux
163 distribution and need to support the above two drivers, or you are
164 certain you need to support some really custom firmware loading
165 facility in userspace.
166
167config FW_LOADER_USER_HELPER_FALLBACK
168 bool "Force the firmware sysfs fallback mechanism when possible"
169 depends on FW_LOADER_USER_HELPER
170 help
171 Enabling this option forces a sysfs userspace fallback mechanism
172 to be used for all firmware requests which explicitly do not disable a
173 a fallback mechanism. Firmware calls which do prohibit a fallback
174 mechanism is request_firmware_direct(). This option is kept for
175 backward compatibility purposes given this precise mechanism can also
176 be enabled by setting the proc sysctl value to true:
177
178 /proc/sys/kernel/firmware_config/force_sysfs_fallback
179
180 If you are unsure about this, say N here.
181
182config FW_LOADER_COMPRESS
183 bool "Enable compressed firmware support"
184 help
185 This option enables the support for loading compressed firmware
186 files. The caller of firmware API receives the decompressed file
187 content. The compressed file is loaded as a fallback, only after
188 loading the raw file failed at first.
189
190 Compressed firmware support does not apply to firmware images
191 that are built into the kernel image (CONFIG_EXTRA_FIRMWARE).
192
193if FW_LOADER_COMPRESS
194config FW_LOADER_COMPRESS_XZ
195 bool "Enable XZ-compressed firmware support"
196 select FW_LOADER_PAGED_BUF
197 select XZ_DEC
198 default y
199 help
200 This option adds the support for XZ-compressed files.
201 The files have to be compressed with either none or crc32
202 integrity check type (pass "-C crc32" option to xz command).
203
204config FW_LOADER_COMPRESS_ZSTD
205 bool "Enable ZSTD-compressed firmware support"
206 select ZSTD_DECOMPRESS
207 help
208 This option adds the support for ZSTD-compressed files.
209
210endif # FW_LOADER_COMPRESS
211
212config FW_CACHE
213 bool "Enable firmware caching during suspend"
214 depends on PM_SLEEP
215 default y if PM_SLEEP
216 help
217 Because firmware caching generates uevent messages that are sent
218 over a netlink socket, it can prevent suspend on many platforms.
219 It is also not always useful, so on such platforms we have the
220 option.
221
222 If unsure, say Y.
223
224config FW_UPLOAD
225 bool "Enable users to initiate firmware updates using sysfs"
226 select FW_LOADER_SYSFS
227 select FW_LOADER_PAGED_BUF
228 help
229 Enabling this option will allow device drivers to expose a persistent
230 sysfs interface that allows firmware updates to be initiated from
231 userspace. For example, FPGA based PCIe cards load firmware and FPGA
232 images from local FLASH when the card boots. The images in FLASH may
233 be updated with new images provided by the user. Enable this device
234 to support cards that rely on user-initiated updates for firmware files.
235
236 If unsure, say N.
237
238endif # FW_LOADER
239endmenu